> 400MHz G4 [...] model may not be supported, as the team only has enough
> resources to support a limited number of G4 PowerMacs and they have been
> working on the later models first.

If this 400 MHz PowerMac G4 is a "Sawtooth" model (aka "AGP Graphics") it may be supported. And even without 3rd party accelerator, I guess.
I don't know if support for "Sawtooth" would include support for "Gigabit Ethernet" model as well, though.

Refer to:
https://morph.zone/modules/newbb_plus/viewtopic.php?topic_id=6910&forum=11#71006 (second link therein)